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Man Pages

Manual Reference Pages  -  IO::STTY (3)

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Change and print terminal line settings



    # calling the script directly [setting...] {-a,-g,-v,--version}
    # Calling Stty module
    use IO::Stty;
    IO::Stty::stty(\*TTYHANDLE, @modes);

     use IO::Stty;

     # Turn off echoing.

     # Do whatever.. grab input maybe?
     $read_password = <>;

     # Now restore the old mode.

     # What settings do we have anyway?
     print IO::Stty::stty(\*STDIN,-a);


This is the PERL POSIX compliant stty.


This has not been tailored to the IO::File stuff but will work with it as indicated. Before you go futzing with term parameters it’s a good idea to grab the current settings and restore them when you finish.

stty accepts the following non-option arguments that change aspects of the terminal line operation. A ‘[-]’ before a capability means that it can be turned off by preceding it with a ‘-’.

stty parameters

    Control settings

[-]parenb Generate parity bit in output and expect parity bit in input.
[-]parodd Set odd parity (even with ‘-’).
cs5 cs6 cs7 cs8 Set character size to 5, 6, 7, or 8 bits.
[-]hupcl [-]hup Send a hangup signal when the last process closes the tty.
[-]cstopb Use two stop bits per character (one with ‘-’).
[-]cread Allow input to be received.
[-]clocal Disable modem control signals.

    Input settings

[-]ignbrk Ignore break characters.
[-]brkint Breaks cause an interrupt signal.
[-]ignpar Ignore characters with parity errors.
[-]parmrk Mark parity errors (with a 255-0-character sequence).
[-]inpck Enable input parity checking.
[-]istrip Clear high (8th) bit of input characters.
[-]inlcr Translate newline to carriage return.
[-]igncr Ignore carriage return.
[-]icrnl Translate carriage return to newline.
[-]ixon Enable XON/XOFF flow control.
[-]ixoff Enable sending of stop character when the system input buffer is almost full, and start character when it becomes almost empty again.

    Output settings

[-]opost Postprocess output.

    Local settings

[-]isig Enable interrupt, quit, and suspend special characters.
[-]icanon Enable erase, kill, werase, and rprnt special characters.
[-]echo Echo input characters.
[-]echoe, [-]crterase Echo erase characters as backspace-space-backspace.
[-]echok Echo a newline after a kill character.
[-]echonl Echo newline even if not echoing other characters.
[-]noflsh Disable flushing after interrupt and quit special characters.

* Though this claims non-posixhood it is supported by the perl

[-]tostop (np) Stop background jobs that try to write to the terminal.

    Combination settings

ek Reset the erase and kill special characters to their default values.
sane Same as:

    cread -ignbrk brkint -inlcr -igncr icrnl -ixoff opost
    isig icanon echo echoe echok -echonl -noflsh -tostop

also sets all special characters to their default values.

[-]cooked Same as:

    brkint ignpar istrip icrnl ixon opost isig icanon

plus sets the eof and eol characters to their default values if they are the same as the min and time characters. With ‘-’, same as raw.

[-]raw Same as:

    -ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr
    -icrnl -ixon -ixoff -opost -isig -icanon min 1 time 0

With ‘-’, same as cooked.

[-]pass8 Same as:

    -parenb -istrip cs8

With ‘-’, same as parenb istrip cs7.

dec Same as:

    echoe echoctl echoke -ixany

Also sets the interrupt special character to Ctrl-C, erase to Del, and kill to Ctrl-U.

    Special characters

The special characters’ default values vary from system to system. They are set with the syntax ‘name value’, where the names are listed below and the value can be given either literally, in hat notation (‘^c’), or as an integer which may start with ‘0x’ to indicate hexadecimal, ‘0’ to indicate octal, or any other digit to indicate decimal. Giving a value of ‘^-’ or ‘undef’ disables that special character.
intr Send an interrupt signal.
quit Send a quit signal.
erase Erase the last character typed.
kill Erase the current line.
eof Send an end of file (terminate the input).
eol End the line.
start Restart the output after stopping it.
stop Stop the output.
susp Send a terminal stop signal.

    Special settings

min N Set the minimum number of characters that will satisfy a read until the time value has expired, when <E>-icanon<E> is set.
time N Set the number of tenths of a second before reads time out if the min number of characters have not been read, when -icanon is set.
N Set the input and output speeds to N. N can be one of: 0 50 75 110 134 134.5 150 200 300 600 1200 1800 2400 4800 9600 19200 38400 exta extb. exta is the same as 19200; extb is the same as 38400. 0 hangs up the line if -clocal is set.


-a Print all current settings in human-readable form.
-g Print all current settings in a form that can be used as an argument to another stty command to restore the current settings.
-v,--version Print version info.

Direct Subroutines


    IO::Stty::stty(\*STDIN, @params);

From comments:

    Im not feeling very inspired about this. Terminal parameters are obscure
    and boring. Basically what this will do is get the current setting,
    take the parameters, modify the setting and write it back. Zzzz.
    This is not especially efficent and probably not too fast. Assuming the POSIX
    spec has been implemented properly it should mostly work.

<B>B>show_me_the_crap()<B>B> Needs documentation


Austin Schutz <> (Initial version and maintenance)

Todd Rinaldo <> (Maintenance)


This is use at your own risk software. Do anything you want with it except blame me for it blowing up your machine because it’s full of bugs.

See above for what functions are supported. It’s mostly standard POSIX stuff. If any of the settings are wrong and you actually know what some of these extremely arcane settings (like what ’sane’ should be in POSIX land) really should be, please open an RT ticket.




Copyright 1997 Austin Schutz, all rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

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